81561243 has 16 divisors (see below), whose sum is σ = 119450880. Its totient is φ = 49271904.

The previous prime is 81561229. The next prime is 81561269. The reversal of 81561243 is 34216518.

It is not a de Polignac number, because 81561243 - 2¹⁷ = 81430171 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 81561243.

It is not an unprimeable number, because it can be changed into a prime (81561143) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29796 + ... + 32417.

It is an arithmetic number, because the mean of its divisors is an integer number (7465680).

Almost surely, 2^81561243 is an apocalyptic number.

81561243 is a deficient number, since it is larger than the sum of its proper divisors (37889637).

81561243 is a wasteful number, since it uses less digits than its factorization.

81561243 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 62258.

The product of its digits is 5760, while the sum is 30.

The square root of 81561243 is about 9031.1263417140. The cubic root of 81561243 is about 433.6718958993.

The spelling of 81561243 in words is "eighty-one million, five hundred sixty-one thousand, two hundred forty-three".